Inactivates link when Y is out of Element bounds
Inactivates link when Y is out of Element bounds

Also ``top`` and ``height`` variables renamed to more consistent ``elemTopBound`` and ``elemBottomBound`` correspondently.

ntdb/react-scroll,slashtu/react-scroll,daviferreira/react-scroll,synapsestudios/react-scroll,vanderlin/react-scroll,fisshy/react-scroll